Cyclopropyl amines as modulators of the histamine H3 receptor

ABSTRACT

Certain cyclopropyl amines are histamine H 3  modulators useful in the treatment of histamine H 3  receptor mediated diseases.

RELATED APPLICATIONS

This application claims the benefit under 35 USC § 119(e) of provisionalapplication Ser. No. 60/717,659, filed Sep. 16, 2005, which isincorporated herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a series of cyclopropyl amines, theirsynthesis, and methods for using them to treat disorders and conditionsin which the histamine H₃ receptor is involved. As a consequence ofthese activities, the compounds of the present invention will havetherapeutic utility for the treatment of a variety of CNS relateddisorders including, but not limited to, narcolepsy, sleep disorders,obesity, neurodegenerative disorders, cognitive disorders, andhyperactivity disorders.

BACKGROUND OF THE INVENTION

Histamine {2-(imidazol-4-yl)ethylamine} is a biologically-activemolecule. Histamine exerts a physiological effect via multiple distinctG-protein coupled receptors. The histamine H₃ receptor was firstdescribed as a presynaptic autoreceptor in the central nervous system(CNS) (Arrang, J.-M. et al., Nature 1983, 302, 832-837) controlling thesynthesis and release of histamine. Evidence has emerged showing that H₃receptors are also located presynaptically as heteroreceptors onserotonergic, noradrenergic, dopaminergic, cholinergic, and GABAergic(gamma-aminobutyric acid containing) neurons. These H₃ receptors havealso recently been identified in peripheral tissues such as vascularsmooth muscle. Consequently, there are many potential therapeuticapplications for histamine H₃ agonists, antagonists, and inverseagonists. (See: “The Histamine H₃ Receptor-A Target for New Drugs”,Leurs, R. and Timmerman, H., (Eds.), Elsevier, 1998; Morisset, S. etal., Nature 2000, 408, 860-864.)

Several indications for histamine H₃ antagonists and inverse agonistshave similarly been proposed based on animal pharmacology and otherexperiments with known histamine H₃ antagonists (e.g. thioperamide).These include dementia, Alzheimer's disease (Panula, P. et al., Soc.Neurosci. Abstr. 1995, 21, 1977), epilepsy (Yokoyama, H. et al., Eur. J.Pharmacol. 1993, 234, 129-133), narcolepsy, with or without associatedcataplexy, cataplexy, disorders of sleep/wake homeostasis, idiopathicsomnolence, excessive daytime sleepiness (EDS), circadian rhythmdisorders, sleep/fatigue disorders, fatigue, drowsiness associated withsleep apnea, sleep impairment due to perimenopausal hormonal shifts, jetlag, Parkinson's-related fatigue, multiple sclerosis (MS)-relatedfatigue, depression-related fatigue, chemotherapy-induced fatigue,eating disorders (Machidori, H. et al., Brain Res. 1992, 590, 180-186),motion sickness, vertigo, attention deficit hyperactivity disorders(ADHD), learning and memory (Barnes, J. C. et al., Soc. Neurosci. Abstr.1993, 19, 1813), and schizophrenia (Schlicker, E. and Marr, I.,Naunyn-Schmiedeberg's Arch. Pharmacol. 1996, 353, 290-294). (Also see:Stark, H. et al., Drugs Future 1996, 21(5), 507-520; and Leurs, R. etal., Prog. Drug Res. 1995, 45, 107-165 and references cited therein.)Histamine H₃ antagonists, alone or in combination with a histamine H₁antagonist, are reported to be useful for the treatment of upper airwayallergic responses (U.S. Pat. Nos. 5,217,986; 5,352,707 and 5,869,479).A more recent review of this topic was presented by Tozer and Kalindjian(Exp. Opin. Ther. Patents 2000, 10, 1045). For additional reviews, see:Celanire, S. Drug Discovery Today 2005, 10(23/24), 1613-1627; Hancock,A. A. Biochem. Pharmacol. 2006, 71, 1103-1113.

The compounds of the present invention display potency at the human H₃receptor as determined by receptor binding to the human histamine H₃receptor (see Lovenberg, T. W. et al., Mol. Pharmacol. 1999, 55,1101-1107). Screening using the human receptor is particularly importantfor the identification of new therapies for the treatment of humandisease. Conventional binding assays, for example, are determined usingrat synaptosomes (Garbarg, M. et al., J. Pharmacol. Exp. Ther. 1992,263(1), 304-310), rat cortical membranes (West, R. E. et al., Mol.Pharmacol. 1990, 38, 610-613), and guinea pig brain (Korte, A. et al.,Biochem. Biophys. Res. Commun. 1990, 168(3), 979-986). Only limitedstudies have been performed previously using human tissue or the humanreceptor, but these indicate significant differences in the pharmacologyof rodent and primate receptors (West, R. E. et al. Eur. J. Pharmacol.1999, 377, 233-239; Ireland, D. et al. Eur. J. Pharmacol. 2001,433,141-150).

To achieve a desired pharmacological effect, a compound must displaypotency against the biological target, as well as a suitablepharmacokinetic profile. First, the compound must be able to travel toits site of action, whether in the CNS, requiring adequate permeation ofthe blood-brain barrier, or in the periphery. Absorption through variousbiological membranes is dependent on the physical properties of the drug(degree of ionization at physiological pH, partition coefficient,molecular size, among other factors). Once the desired pharmacologicaleffect is produced, a drug must be elimated from the organism at asuitable rate. Where an elimination process is too slow, an accumulationof the drug can occur, potentially causing undesirable side effects.

Various H₃-mediated diseases may require compounds with distinct anddifferent pharmacokinetic profiles. In particular, administration of acompound with a short half-life provides greater control over exposureand duration of action of the drug, which may be advantageous intreating or preventing a particular disease or condition. A compoundwith such an optimized profile allows for the use of tailoredformulations, dosing regimens, and/or delivery strategies to accomplishthese results. For example, a compound with an attenuatedpharmacokinetic profile may produce a shorter pharmacodynamic effect,which may be preferable in treating certain disease states. In contrast,a compound with a long half-life may be preferred for conditions inwhich constant occupancy of the target by the drug, with no or only veryminor changes in drug concentration, are desireable.

Various piperazinyl benzamides were disclosed in U.S. Patent Appl.Publication No. U.S.-2004-0110746-A1 (Jun. 10, 2004), which is herebyincorporated by reference.

The features and advantages of the invention are apparent to one ofordinary skill in the art. Based on this disclosure, including thesummary, detailed description, background, examples, and claims, one ofordinary skill in the art will be able to make modifications andadaptations to various conditions and usages. Publications describedherein are incorporated by reference in their entirety.

Described herein is a series of N-cyclopropyl amine compounds with theability to modulate the activity of the histamine receptor, specificallythe H₃ receptor.

SUMMARY OF THE INVENTION

The invention features a compound selected from the group consisting of:(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone,(4-cyclopropyl-piperazin-1-yl)-[4-(4-fluoro-piperidin-1-ylmethyl)-phenyl]-methanone,(4-cyclopropyl-piperazin-1-yl)-(4-thiomorpholin-4-ylmethyl-phenyl)-methanone,and(4-cyclopropyl-piperazin-1-yl)-[4-(2-hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-methanone,and enantiomers, hydrates, solvates, and pharmaceutically acceptablesalts thereof.

In particular embodiments, the compound is(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonecitrate salt dihydrochloride or(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonecitrate salt. In further embodiments, the compound is(4-cyclopropyl-piperazin-1-yl)-[4-(4-fluoro-piperidin-1-ylmethyl)-phenyl]-methanonecitrate salt,(4-cyclopropyl-piperazin-1-yl)-(4-thiomorpholin-4-ylmethyl-phenyl)-methanonecitrate salt, or(4-cyclopropyl-piperazin-1-yl)-[4-(2-hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-methanonecitrate salt.

The present invention provides methods of treating or preventingdiseases and conditions mediated by histamine H₃ receptor activity. Theinvention also features pharmaceutical compositions containing suchcompounds and methods of using such compositions in the treatment orprevention of diseases mediated by histamine H₃ receptor activity. Thepresent invention also contemplates a method of treating or preventing adisease or condition in which histamine is involved with a combinationtherapy of compounds of the present invention administered with any ofthe following: histamine H₁ antagonists, histamine H₂ antagonists,neurotransmitter re-uptake blockers, selective serotonin re-uptakeinhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors,noradrenergic reuptake inhibitors, non-selective serotonin-, dopamine-or norepinephrine- re-uptake inhibitors, modafinil, and topiramate.

The pK_(a) of a given compound affects the degree of ionization atphysiological pH. As unionized forms are more lipophilic, they canpenetrate membranes, including the blood-brain barrier, more readily.Although calculated pK_(a) values for the a cyclopropyl amine compoundof the present invention (Example 1) were similar to that obtained foran isopropyl analog (Comparative Example 1), the measured pK_(a)'sdiffered greatly. Although it has been suggested that a cyclopropylamine is approximately ten times less basic than aliphatic amines(Zaragoza, et al. J. Med. Chem. 2004, 47, 2833-2838), no directexperimental evidence has been reported (Love, et al. J. Am. Chem. Soc.1968, 90(10), 2455-2462). Therefore, replacement of a cyclopropyl groupfor an aliphatic one may produce a higher fraction of non-protonatedamine at physiological pH and, thus, serve to improve permeability ofmembranes (Zaragoza, et al. J. Med. Chem. 2005, 48, 306-311). These dataindicate that cyclopropyl amines may tend toward a greater permeabilityand volume of distribution (V_(d)) than aliphatic amines of similarstructure.

The present invention provides experimental evidence demonstrating asignificant decrease in basicity for Example 1, a cyclopropyl amine,relative to its isopropyl and cyclobutyl amine analogs. However,cyclopropyl amines of the present invention actually showed apharmacokinetic profile that contrasted with the results predicted inthe literature. For example, Example 1B displayed a shorter half-life(T_(1/2)) and lower volume of distribution (V_(d)) than ComparativeExamples 1B and 2B. Similarly, Example 2B displayed a shorter T_(1/2)and lower V_(d) than Comparative Examples 3B and 4B; Example 3Bdisplayed a shorter T_(1/2) and lower V_(d) than Comparative Example 5B,and Example 4B displayed a shorter T_(1/2) and lower V_(d) thanComparative Example 6B.

Additional features and advantages of the invention will become apparentfrom the detailed description and examples below, and the appendedclaims.

DETAILED DESCRIPTION OF THE INVENTION

The invention may be more fully appreciated by reference to thefollowing description, including the following glossary of terms and theconcluding examples. For the sake of brevity, the disclosures of thepublications cited in this specification are herein incorporated byreference.

As used herein, the terms “including”, “containing” and “comprising” areused herein in their open, non-limiting sense.

Isomeric forms of the compounds of the present invention, and of theirpharmaceutically acceptable salts, are encompassed within the presentinvention, and reference herein to one of such isomeric forms is meantto refer to at least one of such isomeric forms. One of ordinary skillin the art will recognize that compounds according to this invention mayexist, for example in a single isomeric form whereas other compounds mayexist in the form of an isomeric mixture. For example, the presentinvention encompasses optical isomers of the compounds described herein,including enantiomers and mixtures thereof. In addition, certaincompounds referred to herein can exist in solvated or hydrated forms aswell as unsolvated forms. It is understood that this inventionencompasses all such solvated and unsolvated forms of the compounds ofthis invention.

Compounds according to the present invention that have been modified tobe detectable by some analytic technique are also within the scope ofthis invention. The compounds of the present invention may be labeledwith radioactive elements such as ¹²⁵I, ¹⁸F, ¹¹C, ⁶⁴Cu, ³H, ¹⁴C, and thelike for use in imaging or for radioactive treatment of patients. Anexample of such compounds is an isotopically labeled compound, such asan ¹⁸F isotopically labeled compound that may be used as a probe indetection and/or imaging techniques, such as positron emissiontomography (PET) and single-photon emission computed tomography (SPECT).Preferably, compounds of the present invention labeled with ¹⁸F or ¹¹Cmay be used as a positron emission tomography (PET) molecular probe forstudying histamine-mediated disorders. Alternatively, compounds of thepresent invention labeled with ¹⁴C may be used in metabolic studies.Another example of such compounds is an isotopically labeled compound,such as a deuterium and/or tritium labeled compound, that may be used inreaction kinetic studies. The compounds described herein may be reactedwith an appropriate functionalized radioactive reagents usingconventional chemistry to provide radiolabeled compounds.

The compounds as described above may be made according to processeswithin the skill of the art and/or that are described in the schemes andexamples that follow. To obtain the various compounds herein, startingmaterials may be employed that carry the ultimately desired substituentsthough the reaction scheme with or without protection as appropriate.This may be achieved by means of conventional protecting groups, such asthose described in “Protective Groups in Organic Chemistry”, ed. J. F.W. McOmie, Plenum Press, 1973; and T. W. Greene & P. G. M. Wuts,“Protective Groups in Organic Synthesis”, 3^(rd) ed., John Wiley & Sons,1999. The protecting groups may be removed at a convenient subsequentstage using methods known from the art. Alternatively, it may benecessary to employ, in the place of the ultimately desired substituent,a suitable group that may be carried through the reaction scheme andreplaced as appropriate with the desired substituent. Such compounds,precursors, or prodrugs are also within the scope of the invention.Reactions may be performed between the melting point and the refluxtemperature of the solvent, and preferably between 0° C. and the refluxtemperature of the solvent.

The compounds as described above may be made according to Schemes A-Cbelow. Persons skilled in the art will recognize that certain compoundsare more advantageously produced by one scheme as compared to the other.In addition, synthetic sequences described in U.S. patent applicationSer. No. 10/690,115 are hereby incorporated by reference and may beapplied to the preparation of compounds of the present invention. Oneskilled in the art will recognize that compounds of Formula (I) wherewhere R¹R²N— is morpholinyl, 4-fluoropiperidinyl, thiomorpholinyl, or2-hydroxymethyl-morpholin-4-yl are compounds of the present invention.

Referring to Scheme A, amines of formula (X), where PG is cyclopropyl ora suitable protecting group such as a benzyl or tert-butylcarbamoyl(Boc), may be coupled with benzoic acids of formula (XI), either throughactivation of the acid to the acid chloride or acid fluoride followed byreaction with the amine, or directly under peptide coupling conditions,such as 1,1′-carbonyldiimidazole (CDI) or1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride(EDC)/1-hydroxybenzotriazole (HOBt). Preferably, reactions are run withEDC/HOBt in the presence of 4-(dimethylamino)pyridine (DMAP), in asolvent such as CH₂Cl₂. Benzaldehydes of formula (XII) may then bereacted with suitable amines R¹NR²H (where R¹NR²H is morpholine,4-fluoropiperidine, thiomorpholine, or morpholin-2-yl-methanol) underreductive animation conditions to provide benzyl amines (XIII). Suitablereducing agents include NaCNBH₃ or NaB(OAc)₃H in a solvent such asmethanol or dichloroethane. Preferred conditions include NaB(OAc)₃H inmethanol. The protecting group “PG” may then be removed under standarddeprotection conditions to provide amines of formula (XIV). Where PG isBoc, deprotection may be effected using HCl in 1,4-dioxane ortrifluoroacetic acid (TFA) in CH₂Cl₂. Amines (XV) are converted to thecorresponding cyclopropyl amines of Formula (I) through reaction with[(1-methoxycyclopropyl)oxy]trimethylsilane or[(1-ethoxycyclopropyl)oxy]-trimethylsilane (R is methyl or ethyl) underconditions similar to those described in J. Med. Chem. 2004, 47(11),2833-2838 and Tetrahedron Lett. 1995, 36(41), 7399-7402.

Alternatively, compounds of the present invention may be prepared as inSchemes B and C. To this end, protected heterocycle (X), where PG is asdefined previously, may be reacted with[(1-methoxycyclopropyl)oxy]-trimethylsilane or[(1-ethoxycyclopropyl)oxy]trimethylsilane as described in J. Med. Chem.2004, 47(11), 2833-2838 and Tetrahedron Lett. 1995, 36(41), 7399-7402.Preferably, PG is a Boc group. The group “PG” may then be removed understandard deprotection conditions to provide cyclopropyl amines offormula (XVI). Where PG is Boc, preferred conditions include a mixtureof HCl in a solvent such as 1,4-dioxane.

Acids of formula (XI) may be coupled (through activation or directly asdescribed in Scheme A) with amines (XVI) to form amides (XVII).Reductive animation with a suitable amine as described in Scheme A givesrise to compounds of Formula (I).

Compounds of the present invention may be converted to theircorresponding salts using methods known to those skilled in the art. Forexample, free base forms of compounds of the present invention may betreated with TFA, HCl, or citric acid in a solvent such as methanol(MeOH) or ethanol (EtOH) to provide the corresponding salt forms.

Compounds prepared according to the schemes described above may beobtained as single enantiomers or diastereomers, or as racemic mixturesor mixtures of enantiomers or diastereomers. Where such mixtures areobtained, isomers may be separated using conventional methods such aschromatography or crystallization. Where racemic (1:1) and non-racemic(not 1:1) mixtures of enantiomers are obtained, single enantiomers maybe isolated using conventional separation methods known to one skilledin the art. Particularly useful separation methods may include chiralchromatography, recrystallization, resolution, diastereomeric saltformation, or derivatization into diastereomeric adducts followed byseparation.

The present invention includes within its scope prodrugs of thecompounds of this invention. In general, such prodrugs will befunctional derivatives of the compounds that are readily convertible invivo into the required compound. Thus, in the methods of treatment ofthe present invention, the term “administering” shall encompass thetreatment of the various disorders described with a compound of thepresent invention or with a compound that converts to a compound of thepresent invention in vivo after administration to the patient.Conventional procedures for the selection and preparation of suitableprodrug derivatives are described, for example, in “Design of Prodrugs”,ed. H. Bundgaard, Elsevier, 1985. In addition to salts, the inventionprovides the esters, amides, and other protected or derivatized forms ofthe described compounds.

For therapeutic use, salts of the compounds of the present invention arethose that are pharmaceutically acceptable. However, salts of acids andbases that are non-pharmaceutically acceptable may also find use, forexample, in the preparation or purification of a pharmaceuticallyacceptable compound. All salts, whether pharmaceutically acceptable ornot, are included within the ambit of the present invention.

Pharmaceutically acceptable salts of compounds according to the presentinvention refer to those salt forms of the compounds of the presentinvention which would be apparent to the pharmaceutical chemist, i.e.,those that are non-toxic and that would favorably affect thepharmacokinetic properties of said compounds of the present invention,such as sufficient palatability, absorption, distribution, metabolismand excretion. Other factors, more practical in nature, which are alsoimportant in the selection, are cost of raw materials, ease ofcrystallization, yield, stability, hygroscopicity and flowability of theresulting bulk drug.

Examples of acids that may be used in the preparation ofpharmaceutically acceptable salts include the following: acetic acid,2,2-dichloroacetic acid, acylated amino acids, adipic acid, alginicacid, ascorbic acid, L-aspartic acid, benzenesulfonic acid, benzoicacid, 4-acetamidobenzoic acid, boric acid, (+)-camphoric acid,camphorsulfonic acid, (+)-(1S)-camphor-10-sulfonic acid, capric acid,caproic acid, caprylic acid, cinnamic acid, citric acid, cyclamic acid,cyclohexanesulfamic acid, dodecylsulfuric acid, ethane-1,2-disulfonicacid, ethanesulfonic acid, 2-hydroxy-ethanesulfonic acid, formic acid,fumaric acid, galactaric acid, gentisic acid, glucoheptonic acid,D-gluconic acid, D-glucuronic acid, L-glutamic acid, α-oxo-glutaricacid, glycolic acid, hippuric acid, hydrobromic acid, hydrochloric acid,hydroiodic acid, (+)-L-lactic acid, (±)-DL-lactic acid, lactobionicacid, lauric acid, maleic acid, (-)-L-malic acid, malonic acid,(±)-DL-mandelic acid, methanesulfonic acid, naphthalene-2-sulfonic acid,naphthalene-1,5-disulfonic acid, 1-hydroxy-2-naphthoic acid, nicotinicacid, nitric acid, oleic acid, orotic acid, oxalic acid, palmitic acid,pamoic acid, perchloric acid, phosphoric acid, L-pyroglutamic acid,saccharic acid, salicylic acid, 4-amino-salicylic acid, sebacic acid,stearic acid, succinic acid, sulfuric acid, tannic acid, (+)-L-tartaricacid, thiocyanic acid, p-toluenesulfonic acid, undecylenic acid, andvaleric acid.

Compounds of the present invention containing acidic protons may beconverted into their therapeutically active non-toxic metal or amineaddition salt forms by treatment with appropriate organic and inorganicbases. Appropriate base salt forms comprise, for example, the ammoniumsalts; the alkali and earth alkaline metal salts (e.g. lithium, sodium,potassium, magnesium, calcium salts, which may be prepared by treatmentwith, for example, magnesium hydroxide, calcium hydroxide, potassiumhydroxide, zinc hydroxide, or sodium hydroxide); and amine salts madewith organic bases (e.g. primary, secondary and tertiary aliphatic andaromatic amines such as L-arginine, benethamine, benzathine, choline,deanol, diethanolamine, diethylamine, dimethylamine, dipropylamine,diisopropylamine, 2-(diethylamino)-ethanol, ethanolamine, ethylamine,ethylenediamine, isopropylamine, N-methyl-glucamine, hydrabamine,1H-imidazole, L-lysine, morpholine, 4-(2-hydroxyethyl)-morpholine,methylamine, piperidine, piperazine, propylamine, pyrrolidine,1-(2-hydroxyethyl)-pyrrolidine, pyridine, quinuclidine, quinoline,isoquinoline, secondary amines, triethanolamine, trimethylamine,triethylamine, N-methyl-D-glucamine,2-amino-2-(hydroxymethyl)-1,3-propanediol, and tromethamine). See, e.g.,S. M. Berge, et al., “Pharmaceutical Salts”, J. Pharm. Sci., 1977,66:1-19, and Handbook of Pharmaceutical Salts, Properties, Selection,and Use; Stahl, P. H., Wermuth, C. G., Eds.; Wiley-VCH and VHCA: Zurich,2002, which are incorporated herein by reference.

The compounds of the present invention are modulators of the histamineH₃ receptor, and as such, the compounds are useful in the treatment ofdisease states mediated by histamine H₃ receptor activity. Thus, thecompounds of the present invention may be used in a method of treating asubject suffering from or diagnosed with a disease mediated by histamineH₃ receptor activity, comprising administering to a subject in need ofsuch treatment an effective amount of a compound of the presentinvention, or a pharmaceutically acceptable salt thereof. Particularly,the compounds may be used in methods for treating or preventingneurologic or neuropsychiatric disorders including sleep/wake andarousal/vigilance disorders (e.g. insomnia and jet lag), attentiondeficit hyperactivity disorders (ADHD), learning and memory disorders,cognitive dysfunction, migraine, neurogenic inflammation, dementia, mildcognitive impairment (pre-dementia), Alzheimer's disease, epilepsy,narcolepsy with or without associated cataplexy, cataplexy, disorders ofsleep/wake homeostasis, idiopathic somnolence, excessive daytimesleepiness (EDS), circadian rhythm disorders, sleep/fatigue disorders,fatigue, drowsiness associated with sleep apnea, sleep impairment due toperimenopausal hormonal shifts, Parkinson's-related fatigue, MS-relatedfatigue, depression-related fatigue, chemotherapy-induced fatigue,eating disorders, obesity, motion sickness, vertigo, schizophrenia,substance abuse, bipolar disorders, manic disorders and depression, aswell as other disorders in which the histamine H₃ receptor is involved,such as upper airway allergic response, asthma, itch, nasal congestionand allergic rhinitis in a subject in need thereof. For example, theinvention features methods for preventing, inhibiting the progressionof, or treating upper airway allergic response, asthma, itch, nasalcongestion and allergic rhinitis. Excessive daytime sleepiness (EDS) mayoccur with or without associated sleep apnea, shift work, fibromyalgia,MS, and the like.

The compounds of the present invention may be used in methods fortreating or preventing disease states selected from the group consistingof: cognitive disorders, sleep disorders, psychiatric disorders, andother disorders.

Cognitive disorders include, for example, dementia, Alzheimer's disease(Panula, P. et al., Soc. Neurosci. Abstr. 1995, 21, 1977), cognitivedysfunction, mild cognitive impairment (pre-dementia), attention deficithyperactivity disorders (ADHD), attention-deficit disorders, andlearning and memory disorders (Barnes, J. C. et al., Soc. Neurosci.Abstr. 1993, 19, 1813). Learning and memory disorders include, forexample, learning impairment, memory impairment, age-related cognitivedecline, and memory loss. H₃ antagonists have been shown to improvememory in a variety of memory tests, including the elevated plus maze inmice (Miyazaki, S. et al. Life Sci. 1995, 57(23), 2137-2144), atwo-trial place recognition task (Orsetti, M. et al. Behav. Brain Res.2001, 124(2), 235-242), the passive avoidance test in mice (Miyazaki, S.et al. Meth. Find. Exp. Clin. Pharmacol. 1995, 17(10), 653-658) and theradial maze in rats (Chen, Z. Acta Pharmacol. Sin. 2000, 21(10),905-910). Also, in the spontaneously hypertensive rat, an animal modelfor the learning impairments in attention-deficit disorders, H₃antagonists were shown to improve memory (Fox, G. B. et al. Behav. BrainRes. 2002, 131(1-2), 151-161).

Sleep disorders include, for example, insomnia, disturbed sleep,narcolepsy (with or without associated cataplexy), cataplexy, disordersof sleep/wake homeostasis, idiopathic somnolence, excessive daytimesleepiness (EDS), circadian rhythm disorders, fatigue, lethargy,REM-behavioral disorder, and jet lag. Fatigue and/or sleep impairmentmay be caused by or associated with various sources, such as, forexample, sleep apnea, perimenopausal hormonal shifts, Parkinson'sdisease, multiple sclerosis (MS), depression, chemotherapy, or shiftwork schedules.

Psychiatric disorders include, for example, schizophrenia (Schlicker, E.and Marr, I., Naunyn-Schmiedeberg's Arch. Pharmacol. 1996, 353,290-294), bipolar disorders, manic disorders, depression (Lamberti, C.et al. Br. J. Pharmacol. 1998, 123(7), 1331-1336; Perez-Garcia, C. etal. Psychopharmacology 1999, 142(2), 215-220) (Also see: Stark, H. etal., Drugs Future 1996, 21(5), 507-520; and Leurs, R. et al., Prog. DrugRes. 1995, 45, 107-165 and references cited therein.),obsessive-compulsive disorder, and post-traumatic stress disorder.

Other disorders include, for example, motion sickness, vertigo(including vertigo and benign postural vertigo), tinitus, epilepsy(Yokoyama, H. et al., Eur. J. Pharmacol. 1993, 234, 129-133), migraine,neurogenic inflammation, eating disorders (Machidori, H. et al., BrainRes. 1992, 590, 180-186), obesity, substance abuse disorders, movementdisorders (e.g. restless leg syndrome), and eye-related disorders (e.g.macular degeneration and retinitis pigmentosis).

Said methods of treating and preventing comprise the step ofadministering to a mammal suffering therefrom an effective amount of atleast one compound of the present invention.

The present invention also contemplates a method of treating orpreventing a histamine-mediated disease or condition with a combinationtherapy for the treatment of allergic rhinitis, nasal congestion, andallergic congestion, comprising: a) administering an effective amount ofat least one compound of the present invention, and b) administering aneffective amount of one or more histamine H₁ or H₂ antagonists. Suitablehistamine H₁ antagonists include: loratidine (CLARITIN™), desloratidine(CLARINEX™), fexofenadine (ALLEGRA™) and cetirizine (ZYRTEC™).

The present invention also contemplates a method of treating orpreventing a histamine-mediated disease or condition with a combinationtherapy for the treatment of depression, mood disorders orschizophrenia, comprising: a) administering an effective amount of atleast one compound of the present invention, and b) administering aneffective amount of one or more neurotransmitter re-uptake blockers.Suitable neurotransmitter re-uptake blockers include: selectiveserotonin re-uptake inhibitors (SSRIs), serotonin-norepinephrinereuptake inhibitors, noradrenergic reuptake inhibitors, or non-selectiveserotonin-, dopamine- or norepinephrine re-uptake inhibitors. Particularexamples of neurotransmitter re-uptake blockers include fluoxetine(PROZAC™), sertraline (ZOLOFT™), paroxetine (PAXIL™), and amitryptyline.

The present invention also contemplates a method of treating orpreventing a histamine-mediated disease or condition with a combinationtherapy for the treatment of narcolepsy, excessive daytime sleepiness(EDS), Alzheimer's disease, depression, attention deficit disorders,MS-related fatigue, post-anesthesia grogginess, cognitive impairment,schizophrenia, spasticity associated with cerebral palsy, age-relatedmemory decline, idiopathic somnolence, or jet-lag, comprising: a)administering an effective amount of at least one compound of thepresent invention, and b) administering an effective amount ofmodafinil.

In another embodiment, the present invention contemplates a method oftreating or preventing a histamine-mediated disease or condition with acombination therapy comprising: a) administering an effective amount ofat least one compound of the present invention, and b) administering aneffective amount of topiramate (Topamax). In particular, such methodsare useful for the treatment of obesity. Preferably, the combinationmethod employs doses of topiramate in the range of about 20 to 300 mgper dose.

Compounds of the present invention may be administered in pharmaceuticalcompositions to treat patients (humans and other mammals) with disordersmediated by the H₃ receptor. Thus, the invention features pharmaceuticalcompositions containing at least one compound of the present inventionand a pharmaceutically acceptable carrier. A composition of theinvention may further include at least one other therapeutic agent suchas H₁ antagonists, SSRIs, topiramate, or modafinil (for example, acombination formulation or combination of differently formulated activeagents for use in a combination therapy method).

The present invention also features methods of using or preparing orformulating such pharmaceutical compositions. The pharmaceuticalcompositions can be prepared using conventional pharmaceuticalexcipients and compounding techniques known to those skilled in the artof preparing dosage forms. It is anticipated that the compounds of theinvention can be administered by oral, parenteral, rectal, topical, orocular routes, or by inhalation. Preparations may also be designed togive slow release of the active ingredient. The preparation may be inthe form of tablets, capsules, sachets, vials, powders, granules,lozenges, powders for reconstitution, liquid preparations, orsuppositories. Preferably, compounds may be administered by intravenousinfusion or topical administration, but more preferably by oraladministration.

For oral administration, the compounds of the invention can be providedin the form of tablets or capsules, or as a solution, emulsion, orsuspension. Tablets for oral use may include the active ingredient mixedwith pharmaceutically acceptable excipients such as inert diluents,disintegrating agents, binding agents, lubricating agents, sweeteningagents, flavoring agents, coloring agents and preservatives. Suitableinert fillers include sodium and calcium carbonate, sodium and calciumphosphate, lactose, starch, sugar, glucose, methyl cellulose, magnesiumstearate, mannitol, sorbitol, and the like; typical liquid oralexcipients include ethanol, glycerol, water and the like. Starch,polyvinyl-pyrrolidone, sodium starch glycolate, microcrystallinecellulose, and alginic acid are suitable disintegrating agents. Bindingagents may include starch and gelatin. The lubricating agent, ifpresent, will generally be magnesium stearate, stearic acid or talc. Ifdesired, the tablets may be coated with a material such as glycerylmonostearate or glyceryl distearate to delay absorption in thegastrointestinal tract, or may be coated with an enteric coating.Capsules for oral use include hard gelatin capsules in which the activeingredient is mixed with a solid, semi-solid, or liquid diluent, andsoft gelatin capsules wherein the active ingredient is mixed with water,an oil such as peanut oil or olive oil, liquid paraffin, a mixture ofmono and di-glycerides of short chain fatty acids, polyethylene glycol400, or propylene glycol.

Liquids for oral administration may be suspensions, solutions, emulsionsor syrups or may be presented as a dry product for reconstitution withwater or other suitable vehicles before use. Compositions of such liquidmay contain pharmaceutically-acceptable excipients such as suspendingagents (for example, sorbitol, methyl cellulose, sodium alginate,gelatin, hydroxyethylcellulose, carboxymethylcellulose, aluminiumstearate gel and the like); non-aqueous vehicles, which include oils(for example, almond oil or fractionated coconut oil), propylene glycol,ethyl alcohol or water; preservatives (for example, methyl or propylp-hydroxybenzoate or sorbic acid); wetting agents such as lecithin; and,if needed, flavoring or coloring agents.

The compounds of this invention may also be administered by non-oralroutes. The compositions may be formulated for rectal administration asa suppository. For parenteral use, including intravenous, intramuscular,intraperitoneal, or subcutaneous routes, the compounds of the inventionwill generally be provided in sterile aqueous solutions or suspensions,buffered to an appropriate pH and isotonicity or in parenterallyacceptable oil. Suitable aqueous vehicles include Ringer's solution andisotonic sodium chloride. Such forms will be presented in unit dose formsuch as ampules or disposable injection devices, in multi-dose formssuch as vials from which the appropriate dose may be withdrawn, or in asolid form or pre-concentrate that can be used to prepare an injectableformulation. Another mode of administration of the compounds of theinvention may utilize a patch formulation to affect transdermaldelivery. The compounds of this invention may also be administered byinhalation, via the nasal or oral routes using a spray formulationconsisting of the compound of the invention and a suitable carrier.

Methods are known in the art for determining effective doses fortherapeutic (treatment) and prophylactic (preventative) purposes for thepharmaceutical compositions or the drug combinations of the presentinvention, whether or not formulated in the same composition. Thespecific dosage level required for any particular patient will depend ona number of factors, including severity of the condition being treated,the route of administration, metabolic rate, and the weight of thepatient. For therapeutic purposes, “effective dose” or “effectiveamount” refers to that amount of each active compound or pharmaceuticalagent, alone or in combination, that elicits the biological or medicinalresponse in a tissue system, animal, or human that is being sought by aresearcher, veterinarian, medical doctor, or other clinician, whichincludes alleviation of the symptoms of the disease or disorder beingtreated. For prophylactic purposes (i.e., preventing or inhibiting theonset or progression of a disorder), the term “effective dose” or“effective amount” refers to that amount of each active compound orpharmaceutical agent, alone or in combination, that inhibits in asubject the onset or progression of a disorder as being sought by aresearcher, veterinarian, medical doctor, or other clinician, thedelaying of which disorder is mediated, at least in part, by themodulation of the histamine H₃ receptor. Methods of combination therapyinclude co-administration of a single formulation containing all activeagents; essentially contemporaneous administration of more than oneformulation; and administration of two or more active agents separatelyformulated.

It is anticipated that the daily dose (whether administered as a singledose or as divided doses) will be in the range 0.01 to 1000 mg per day,more usually from 1 to 500 mg per day, and most usually from 10 to 200mg per day. Expressed as dosage per unit body weight, a typical dosewill be expected to be between 0.0001 mg/kg and 15 mg/kg, especiallybetween 0.01 mg/kg and 7 mg/kg, and most especially between 0.15 mg/kgand 2.5 mg/kg.

Preferably, oral doses range from about 0.05 to 200 mg/kg, daily, takenin 1 to 4 separate doses. Some compounds of the invention may be orallydosed in the range of about 0.05 to about 50 mg/kg daily, others may bedosed at 0.05 to about 20 mg/kg daily, while still others may be dosedat 0.1 to about 10 mg/kg daily. Infusion doses can range from about 1 to1000 μg/kg/min of inhibitor, admixed with a pharmaceutical carrier overa period ranging from several minutes to several days. For topicaladministration compounds of the present invention may be mixed with apharmaceutical carrier at a concentration of about 0.1 % to about 10% ofdrug to vehicle.

EXAMPLES

In order to illustrate the invention, the following examples areincluded. These examples do not limit the invention. They are only meantto suggest a method of practicing the invention. Those skilled in theart may find other methods of practicing the invention, which areobvious to them. However, those methods are deemed to be within thescope of this invention.

Chemical Examples and Data

Mass spectra were obtained on an Agilent series 1100 MSD usingelectrospray ionization (ESI) in either positive or negative modes asindicated. Nuclear magnetic resonance (NMR) spectra were obtained on aBruker model DPX400 (400 MHz), DPX500 (500 MHz), or DPX600 (600 MHz)spectrometer. The format of the ¹H NMR data below is: chemical shift inppm down field of the tetramethylsilane reference (multiplicity,coupling constant J in Hz, integration).

Reversed-phase high-pressure liquid chromatography (HPLC) was performedon a Hewlett Packard HPLC, Zorbax Eclipse XDB-C8, 5 μm, 4.6×150 mmcolumn, with a gradient of 1 to 99% acetonitrile/water/0.05% TFA over 8min.

Chemical names were generated using ChemDraw Ultra 6.0.2 (CambridgeSoftCorp., Cambridge, Mass.).

Example 1(4-Cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone

Step A. 4-(4-Formyl-benzoyl)-piperazine-1-carboxylic acid tert-butylester. A suspension of 4-carboxybenzaldehyde (3.10 g) in CH₂Cl₂ wastreated sequentially with piperazine-1-carboxylic acid tert-butyl ester(3.6 g), EDC (3.86 g), HOBt (2.68 g), and DMAP (˜0.020 g). After 18 h,the mixture was extracted with 1 N NaOH and then with 1 N HCl. Theorganic layer was dried (Na₂SO₄) and concentrated to give the titlecompound (5.11 g, 78%). MS (ESI): mass calcd. for C₁₇H₂₂N₂O₄, 318.16;m/z found, 219.3 [(M-100)+H]⁺. ¹H NMR (CDCl₃): 10.04 (s, 1H), 7.93 (d,J=8.2, 2H), 7.54 (d, J=8.1, 2H), 3.82-3.67 (m, 2H), 3.58-3.30 (m, 6H),1.46 (s, 9H).

Step B. 4-(4-Morpholin-4-ylmethyl-benzoyl)-piperazine-1-carboxylic acidtert-butyl ester. A solution of4-(4-formyl-benzoyl)-piperazine-1-carboxylic acid tert-butyl ester (2.06g) in methanol (100 mL) was treated with morpholine (4 mL) andNaB(OAc)₃H (6.98 g, in portions over 1 h). After 3 h, the mixture wasdiluted with satd. aq. NaHCO₃ and extracted with CH₂Cl₂. The organiclayer was dried (Na₂SO₄) and concentrated. The residue was purified bycolumn chromatography (SiO₂) to give the title compound (1.22 g, 48%).MS (ESI): mass calcd. for C₂₁H₃₁N₃O₄, 389.23; m/z found, 390.4 [M+H]⁺.¹H NMR (CDCl₃): 7.39-7.33 (m, 4H), 3.75-3.66 (m, 6H), 3.50 (s, 2H),3.51-3.33 (m, 6H), 2.45-2.41 (m, 4H), 1.46 (s, 9H).

Step C. (4-Morpholin-4-ylmethyl-phenyl)-piperazin-1-yl-methanone. Asolution of 4-(4-morpholin-4-ylmethyl-benzoyl)-piperazine-1-carboxylicacid tert-butyl ester (1.163 g) in CH₂Cl₂ (10 mL) was treated with TFA(˜4 mL). After 30 min, additional TFA (5 mL) was added, and the mixturewas stirred for a further 2 h. The mixture was diluted with diluted withsatd. aq. NaHCO₃ and extracted with CH₂Cl₂. The organic layer was dried(Na₂SO₄) and concentrated. The residue was purified by columnchromatography (SiO₂) to give the title compound (0.255 g, 30%). MS(ESI): mass calcd. for C₁₆H₂₃N₃O₂, 289.18; m/z found, 290.4 [M+H]⁺. ¹HNMR (CDCl₃): 7.41-7.35 (m, 4H), 3.95-3.70 (m, 6H), 3.52 (s, 2H),3.09-2.80 (m, 6H), 2.49-2.42 (m, 4H).

Step D. A solution of(4-morpholin-4-ylmethyl-phenyl)-piperazin-1-yl-methanone (0.128 g) inmethanol (7.5 mL) was treated with(1-ethoxy-cyclopropoxy)-trimethyl-silane (1.5 mL), acetic acid (0.2 mL),and NaBH₃CN (˜400 mg). The mixture was heated at 60° C. for 18 h, andthen was cooled to rt and concentrated. The residue was diluted with 1 NNaOH and extracted with CH₂Cl₂. The organic layer was dried (Na₂SO₄) andconcentrated. The residue was purified by column chromatography (SiO₂)to give the title compound (0.0548 g, 38%). MS (ESI): mass calcd. forC₁₉H₂₇N₃O₂, 329.21; m/z found, 330.4 [M+H]⁺. ¹H NMR (CDCl₃): 7.36 (s,4H), 3.79-3.68 (m, 6H), 3.50 (s, 2H), 3.44-3.32 (m, 2H), 2.74-2.61 (m,2H), 2.60-2.50 (s, 2H), 2.45-2.40 (m, 4H), 1.66-1.62 (m, 1H), 0.49-0.44(m, 2H), 0.44-0.39 (m, 2H).

Alternative Preparation of Example 1.

Step A. tert-Butyl 4-cyclopropylpiperazine-1-carboxylate. A mixture oftert-butyl piperazine-1-carboxylate (75.0 g), tetrahydrofuran (THF) (500mL), methanol (500 mL), [(1-ethoxycyclopropyl)oxy]trimethylsilane (161mL), NaBH₃CN (38.0 g), and acetic acid (37 mL) was heated at 60° C. for5 h. The mixture was cooled to rt, treated with water (30 mL) andstirred for 5 min. The mixture was then treated with 1 N NaOH (130 mL)and was further stirred for 15 min. The mixture was concentrated, andthe remaining aqueous solution was extracted with CH₂Cl₂ (500 mL). Theorganic layer was washed with 1 N NaOH (500 mL). The combined aqueouslayers were extracted with CH₂Cl₂ (150 mL). The combined organic layerswere washed with brine (400 mL), dried (Na₂SO₄), and concentrated togive the title compound as a white solid (92 g, 100%). MS (ESI): masscalcd. for C₁₂H₂₂N₂O₂, 226.17; m/z found, 227.2 [M+H⁺]. ¹H NMR (400 MHz,CDCl₃): 3.39 (t, J=5.0 Hz, 4H), 2.55 (t, J=4.9 Hz, 4H), 1.60 (ddd,J=10.3, 6.5, 3.8 Hz, 1H), 1.46 (s, 9H), 0.49-0.38 (m, 4H).

Step B. 1-Cyclopropylpiperazine dihydrochloride. A solution oftert-butyl 4-cyclopropylpiperazine-1-carboxylate (92 g) in 1,4-dioxane(200 mL) was treated with HCl (4 M in 1,4-dioxane, 500 mL) over 10 minwhile maintaining the temperature below 40° C. After the addition wascomplete, the mixture was heated at 45° C. for 9 h and then was cooledto rt. The thick suspension was diluted with hexanes (400 mL) and wascooled to 10° C. The resulting solid was collected by filtration, washedwith hexanes, and dried to give the title compound as a white solid (78g, 96%). MS (ESI): mass calcd. for C₇H₁₄N₂, 126.12; m/z found, 127.0[M+H⁺]. ¹H NMR (400 MHz, D₂O): 3.65 (br t, J=4.7 Hz, 4H), 3.47 (br t,J=5.5 Hz, 4H), 2.85 (br quintet, J=5.8 Hz, 1H), 0.94 (br s, 2H), 0.92(br s, 2H).

Step C. 4-(4-Cyclopropyl-piperazine-1-carbonyl)-benzaldehyde. A mixtureof 4-formyl-benzoic acid (54.4 g), toluene (500 mL),N,N-dimethylformamide (DMF) (3.6 mL), and thionyl chloride (30.4 mL) washeated at 60° C. for 2 h and then was cooled to 5° C. In a separateflask, a 5° C. mixture of NaOH (50.7 g), water (550 mL), and toluene(150 mL) was treated with 1-cyclopropyl-piperazine dihydrochloride (70.0g) in portions while the temperature was maintained below 10° C. Afterthe addition was complete, the mixture was cooled to 5° C. and treatedwith the crude acyl chloride solution prepared as above at a rate suchthat the temperature did not exceed 10° C. After the addition wascomplete, the mixture was allowed to warm to rt and was stirredovernight. The biphasic mixture was basified to pH ˜10 with 1 N NaOH(300 mL). The layers were separated and the aqueous layer was extractedwith toluene (100 mL×2). The combined organic layers were washed withbrine (200 mL), dried (Na₂SO₄), and concentrated to give the titlecompound as pale yellow viscous oil (56.0 g, 62%). HPLC: R_(T)=5.19 min.MS (ESI): mass calcd. for C₁₅H₁₈N₂O₂, 258.14; m/z found, 258.9 [M+H⁺].¹H NMR (400 MHz, CDCl₃): 10.1 (s, 1H), 7.94 (pseudo d, J=8.2 Hz, 2H),7.56 (pseudo d, J=8.1 Hz, 2H), 3.77 (br s, 2H), 3.33 (br s, 2H), 2.71(br s, 2H), 2.55 (br s, 2H), 1.66 (ddd, J=10.2, 6.6, 3.7 Hz, 1H),0.52-0.46 (m, 2H), 0.45-0.40 (br s, 2H).

Step D.(4-Cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone.To a solution of 4-(4-cyclopropyl-piperazine-1-carbonyl)-benzaldehyde(56.0 g) in 1 ,2-dichloroethane (550 mL) was added morpholine (37.8 mL)dropwise over 5 min. The mixture was cooled to 10° C. and was treatedwith NaB(OAc)₃H (64.3 g) in portions over 1 h. After a further 2 h, themixture was warmed to rt, and a water bath was used to keep thetemperature below 20° C. After 18 h, water (60 mL) was added while thetemperature was kept under 20° C. by the addition of small amounts ofice. After 20 min, the mixture was basified to pH ˜10 with 1 N NaOH (450mL) and the mixture was stirred for 10 min. The layers were separated,and the organic layer was washed with 1 N NaOH (150 mL). The combinedaqueous layers were extracted with CH₂Cl₂ (200 mL). The combined organiclayers were washed with brine (200 mL), dried (Na₂SO₄), and concentratedto give the title compound as pale yellow viscous oil (68.0 g, 95%).HPLC: R_(T)=4.39 min. MS (ESI): mass calcd. for C₁₉H₂₇N₃O₂, 329.21; m/zfound, 330.2 [M+H⁺]. ¹H NMR (400 MHz, CDCl₃): 7.35 (br s, 4H), 3.73 (brs, 2H), 3.69 (t, J=4.6 Hz, 4H), 3.50 (s, 2H), 3.37 (br s, 2H), 2.67 (brs, 2H), 2.53 (br s, 2H), 2.43 (t, J=4.2 Hz, 4H), 1.63 (ddd, J=10.3, 6.7,3.7 Hz, 1H), 0.49-0.43 (m, 2H), 0.42-0.39 (br s, 2H). ¹³C NMR (101 MHz,CDCl₃): 170.6, 140.0, 135.1, 129.5, 127.5, 67.4, 63.4, 54.0, 38.7, 6.3.

Example 1A(4-Cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonedihydrochloride

A solution of(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone(68.0 g) in ethanol (400 mL) was heated to 60° C. and treated with conc.HCl (37.8 mL) dropwise over 40 min. A precipitate started to form after˜20 mL of HCl had been added. After the addition was complete, the thicksuspension was slowly cooled to 20° C. over 3 h. The solid was collectedby filtration, washed with ethanol, and dried at 50° C. overnight in avacuum oven to provide the title compound as a white solid (56.2 g,68%). HPLC: R_(T)=4.30 min. MS (ESI): mass calcd. for C₁₉H₂₇N₃O₂,329.21; m/z found, 330.0 [M+H⁺]. ¹H NMR (400 MHz, D₂O): 7.64 (pseudo d,J=8.3 Hz, 2H), 7.58 (pseudo d, J=8.3 Hz, 2H), 4.44 (br s, 2H), 4.20-3.10(m, 16H), 2.88 (ddd, J=11.2, 6.6, 4.8 Hz, 1H), 1.03-0.98 (m, 4H). ¹³CNMR (101 MHz, D₂O): 172.1, 135.3, 132.2, 130.9, 128.0, 64.0, 60.5, 52.6,52.4, 51.7, 44.8, 39.7, 39.5, 3.9.

Example 1B(4-Cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonecitrate salt

A mixture of(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone(0.476 g, 1.45 mmol) and citric acid (0.281 g, 1.46 mmol) was dilutedwith methanol (˜10 mL). The mixture was heated until homogeneous andthen concentrated. The resulting oil was triturated with ethyl acetateand the solid material that formed was dried under vacuum to yield thecitrate salt (0.760 g).

The compounds in Examples 2-4 were prepared using methods analogous tothose described in the preceding examples, with the appropriatesubstituent changes.

Example 2(4-Cyclopropyl-piperazin-1-yl)-[4-(4-fluoro-piperidin-1-ylmethyl)-phenyl]-methanone

MS (ESI): mass calcd. for C₂₀H₂₈FN₃O, 345.22; m/z found, 346.4 [M+H⁺].¹H NMR (400 MHz, CDCl₃): 7.39-7.33 (m, 4H), 4.78-4.58 (m, 1H), 3.82-3.66(m, 2H), 3.51 (s, 2H), 3.46-3.33 (m, 2H), 2.77-2.49 (m, 6H), 2.43-2.32(m, 2H), 1.97-1.82 (m, 4H), 1.68-1.63 (m, 1H), 0.52-0.38 (m, 4H).

Example 2B(4-Cyclopropyl-piperazin-1-yl)-[4-(4-fluoro-piperidin-1-ylmethyl)-phenyl]-methanonecitrate salt

Example 3(4-Cyclopropyl-piperazin-1-yl)-(4-thiomorpholin-4-ylmethyl-phenyl)-methanone

MS (ESI): mass calcd. for C₁₉H₂₇N₃OS, 345.19; m/z found, 346 [M+H⁺]. ¹HNMR (400 MHz, CDCl₃): 7.37-7.32 (m, 4H), 3.86-3.60 (bm, 2H), 3.53 (s,2H), 3.53-3.25 (bm, 2H), 2.75-2.61 (bm, 10H), 2.61-2.45 (bm, 2H),1.66-1.60 (m, 1H), 0.51-0.44 (m, 2H), 0.44-0.38 (m, 6H).

Example 3B(4-Cyclopropyl-piperazin-1-yl)-(4-thiomorpholin-4-ylmethyl-phenyl)-methanonecitrate salt

Example 4(4-Cyclopropyl-piperazin-1-yl)-[4-(2-hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-methanone

MS (ESI): mass calcd. for C₂₀H₂₉N₃O₃, 359.22; m/z found, 360 [M+H⁺]. ¹HNMR (400 MHz, CDCl₃): 7.39-7.34 (m, 4H), 3.93-3.87 (m, 1H), 3.85-3.25(m, 10H), 2.75-2.45 (bm, 6H), 2.25-2.15 (m, 1H), 2.05-1.93 (m, 2H),1.67-1.60 (m, 1H), 0.52-0.45 (m, 2H), 0.45-0.40 (m, 2H).

Example 4B(4-Cyclopropyl-piperazin-1-yl)-[4-(2-hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-methanonecitrate salt

Comparative Example 1(4-Isopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone

Preparation and analytical data for the title compound was presented inU.S. patent application Ser. No. 10/690,115 (Oct. 21, 2003). Thecorresponding salt forms were prepared as described for Examples 1A and1B.

Comparative Example 1A(4-Isopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonedihydrochloride Comparative Example 1B(4-Isopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonecitrate salt

Comparative Example 2(4-Cyclobutyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone.

The title compound was prepared according to the methods described inExample 1. MS (ESI): mass calcd. for C₂₀H₂₉N₃O₂, 343.23; m/z found,344.4 [M+H⁺]. ¹H NMR (400 MHz, CDCl₃): 7.39-7.32 (m, 4H), 3.87-3.65 (m,6H), 3.66-3.36 (m, 4H), 2.80-2.69 (m, 1H), 2.50-2.18 (m, 8H), 2.08-1.99(m, 2H), 1.93-1.81 (m, 2H), 1.79-1.61 (m, 2H). The corresponding saltforms were prepared as described for Examples 1A and 1B.

Comparative Example 2A(4-Cyclobutyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonedihydrochloride Comparative Example 2B(4-Cyclobutyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonecitrate salt

The compounds in Comparative Examples 3-6 and their corresponding saltforms were prepared using methods analogous to those described in thepreceding examples, with the appropriate substituent changes.

Comparative Example 3[4-(4-Fluoro-piperidin-1-ylmethyl)-phenyl]-(4-isopropyl-piperazin-1-yl)-methanone

MS (ESI): mass calcd. for C₂₀H₃₀FN₃O, 347.24; m/z found, 348.4 [M+H⁺].¹H NMR (400 MHz, CDCl₃): 7.36-7.33 (m, 4H), 4.75-4.59 (m, 1H), 3.84-3.71(m, 2H), 3.50 (s, 2H), 3.49-3.38 (m, 2H), 2.71 (heptet, J=6.6 Hz, 1H),2.64-2.31 (m, 8H), 1.94-1.82 (m, 4H), 1.04 (d, J=6.3 Hz, 6H).

Comparative Example 3B[4-(4-Fluoro-piperidin-1-ylmethyl)-phenyl]-(4-isopropyl-piperazin-1-yl)-methanonecitrate salt

Comparative Example 4(4-Cyclobutyl-piperazin-1-yl)-[4-(4-fluoro-piperidin-1-ylmethyl)-phenyl]-methanone

MS (ESI): mass calcd. for C₂₁H₃₀FN₃O, 359.24; m/z found, 360.4 [M+H⁺].¹H NMR (400 MHz, CDCl₃): 7.38-7.34 (m 4H), 4.77-4.60 (m, 1H), 3.88-3.72(m, 2H), 3.52 (s, 2H), 3.51-3.37 (m, 2H), 2.80-2.71 (m, 1H, 2.63-2.54(m, 2H), 2.46-2.20 (m, 6H), 2.09-2.01 (m, 2H), 1.97-1.64 (m, 8H).

Comparative Example 4B(4-Cyclobutyl-piperazin-1-yl)-[4-(4-fluoro-piperidin-1-ylmethyl)-phenyl]-methanonecitrate salt

Comparative Example 5(4-Cyclobutyl-piperazin-1-yl)-(4-thiomorpholin-4-ylmethyl-phenyl)-methanone

MS (ESI): mass calcd. for C₂₀H₂₉N₃OS, 359.20; m/z found, 360 [M+H⁺]. ¹HNMR (400 MHz, CDCl₃): 7.37-7.32 (m, 4H), 3.88-3.65 (bm, 2H), 3.52 (s,2H), 3.52-3.35 (bm, 2H), 2.80-2.63 (bm, 9H), 2.45-2.28 (bm, 4H),2.10-1.98 (m, 2H), 1.95-1.79 (m, 2H), 1.78-1.65 (m, 2H).

Comparative Example 5B(4-Cyclobutyl-piperazin-1-yl)-(4-thiomorpholin-4-ylmethyl-phenyl)-methanonecitrate salt

Comparative Example 6[4-(2-Hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-(4-isopropyl-piperazin-1-yl)-methanone

MS (ESI): mass calcd. for C₂₀H₃₁N₃O₃, 361.24; m/z found, 362 [M+H⁺]. ¹HNMR (400 MHz, CDCl₃): 7.38-7.34 (m, 4H), 3.93-3.87 (m, 1H, 3.87-3.35 (m,10H), 2.73 (heptet, J=6.6 Hz, 1H, 2.70-2.62 (m, 2H), 2.62-2.36 (bm, 4H),2.24-2.15 (m, 1H), 2.05-1.92 (bm, 2H), 1.05 (d, J=6.5 Hz, 6H).

Comparative Example 6B[4-(2-Hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-(4-isopropyl-piperazin-1-yl)-methanonecitratae salt

Physical Chemical Data

The measured pK_(a) values for Example 1, a cyclopropyl amine, wassignificantly lower than that predicted through calculation (using thePallas software package from CompuDrug, Inc.), and also weresignificantly lower than that observed for Comparative Example 1(isopropyl amine). Measured pK_(a), log P, and log D values weredetermined by pION, Inc. (Woburn, Mass.).

TABLE 1 Physical Chemical Data EX pK_(a) (calc.) pK_(a) (meas.) log Plog D Ex. 1 8.5, 6.2 6.5, 5.3 0.89 0.86 Comp. Ex. 1 8.5, 6.2 7.6, 6.20.55 0.13 Comp. Ex. 2 7.8, 6.2 7.4, 6.5 2.09 1.77Biological Examples and DataA. Transfection of Cells with Human Histamine Receptor

Cells were grown to about 70% to 80% confluence and removed from theplate with trypsin and pelleted in a clinical centrifuge. The pellet wasthen re-suspended in 400 μL of complete media and transferred to anelectroporation cuvette with a 0.4 cm gap between the electrodes(Bio-Rad #165-2088). One μg supercoiled H₃ receptor cDNA was added tothe cells and mixed gently. The voltage for the electroporation was setat 0.25 kV and the capacitance was set at 960 μF. After electroporationthe cells were diluted with 10 mL of complete media and were plated ontofour 10 cm dishes at the following ratios: 1:20, 1:10, 1:5, and 1:2. Thecells were allowed to recover for 24 h before adding 600 μg G-418.Colonies that survived selection were grown and tested. SK-N-MC cellswere used because they give efficient coupling for inhibition ofadenylate cyclase. The clones that gave the most robust inhibition ofadenylate cyclase in response to histamine were used for further study.

B. [³H]-N-Methylhistamine Binding

Cell pellets from histamine H₃ receptor-expressing SK-N-MC cells werehomogenized in 50 mM TrisHCl/0.5 mM EDTA. Supernatants from an 800 gspin were collected and were recentrifuged at 30,000 g for 30 min.Pellets were re-homogenized in 50 mM Tris/5 mM EDTA (pH 7.4). Membraneswere incubated with 0.8 nM [³H]-N-methylhistamine plus/minus testcompounds for 60 min at 25° C. and were harvested by rapid filtrationover GF/C glass fiber filters (pretreated with 0.3% polyethylenimine)followed by four washes with buffer. Filters were added to 5 mL ofscintillation cocktail, and the signal was then counted on a liquidscintillation counter. Non-specific binding was defined with 10 μMhistamine. pK_(i) values were calculated based on a K_(D) of 0.8 nM anda ligand concentration ([L]) of 0.8 nM according to the formulaK_(i)=(IC₅₀)/(1+([L]/(KD)). Data for compounds tested in this assay arepresented in Table 2 as an average of results obtained. Binding data forComparative Example 1 was presented in U.S. patent application Ser. No.10/690,115 (Oct. 21, 2003).

TABLE 2 Binding Activity at the Human H₃ Receptor. Ex. K_(i) (nM) pK_(i)Example 1 5.4 8.3 Example 1B 6.5 8.2 Example 2 2.0 8.7 Example 2B 2.08.7 Example 3 2.5 8.6 Example 4 6.0 8.2 Example 4B 23 7.6 ComparativeExample 2 1.0 9.0 Comparative Example 2A 1.7 8.8 Comparative Example 2B2.0 8.7 Comparative Example 3 2.0 8.7 Comparative Example 3B 1.0 9.0Comparative Example 4 0.7 9.2 Comparative Example 5 1.0 9.0 ComparativeExample 6 6.0 8.2 Comparative Example 6B 5.0 8.3C. Cyclic AMP Accumulation

Sublines of SK-N-MC cells were created that expressed a reporterconstruct and the human H₃ receptor. The pA₂ values were obtained asdescribed by Barbier, A. J. et al. (Br. J. Pharmacol. 1994, 143(5),649-661). Data for compounds tested in this assay are presented in Table3, as an average of the results obtained.

TABLE 3 Functional Activity Ex. pA₂ Example 1 8.4 Example 2B 9.0Comparative Example 1 9.0 Comparative Example 1A 8.9 Comparative Example2 9.5 Comparative Example 3B 9.6 Comparative Example 4 10.0 ComparativeExample 6 8.2D. Pharmacokinetics and Bioanalysis

One group of six male Sprague Dawley Rats (approx. 300 g body weight;three animals per time point) was used. They were group-housed, providedfood and water ad libitum, and were maintained on a 12-h light and darkcycle. Animals were acclimatized for at least 7 days after receipt fromthe vendor prior to investigations.

For oral dosing, test compounds were formulated at 1 mg/mL in 0.5%hydroxypropyl methyl cellulose and delivered at a dose of 10 mg/kg.Citric acid salt forms (prepared as described for Example 1B) of thetest compounds were used. Animals received a bolus dose of 10 mg/kg (10mL/kg) for each compound via a 16 gauge intragastric gavage. Forintravenous dosing, test compounds were formulated at 1 mg/mL in 5%dextrose in water and dosed at 1 mg/kg (1 mL/kg) with a bolusintravenous dose via a 24-gauge Terumo® Surflo® catheter in the lateraltail vein. All dosing solutions were prepared immediately prior toinjection.

Blood samples (250 μL) were taken from the lateral tail vein intoheparinized Natelson blood collection tubes and expelled into 1.5 mLmicrocentrifuge tubes. The blood samples were centrifuged for 5 min at14,000 rpm in a micro-centrifuge. Plasma was retained and kept in a −20°C. freezer until analysis by LC-MS/MS.

Data analysis was performed using WinNonlin version 3.3 or 4.0.1. Anon-compartmental model (#200 for Extravascular administration and #201for i.v.) was used to determine the pharmacokinetic parameters shown inTables 4 and 5 (NA=not applicable or not determined).

TABLE 4 Pharmacokinetic Profiles in the Rat T_(max) C_(max) AUC_(INF)T_(1/2) CI (mL/ V_(d) Ex. Mode (h) (ng/mL) (h-ng/mL) (h) min/kg) (L/kg)Ex. 1B oral 0.5 2787 8716 3.11 20.2 5.45 i.v. NA 935 777 0.92 21.6 1.72Comp. oral 1.5 1050 9743 4.71 17.1 6.98 Ex. 1B i.v. NA 4113 1560 3.212.8 3.55 Comp. oral  1.33 683 4104 2.89 43.2 10.33 Ex. 2B i.v. NA 285464 1.86 34.8 6.41

TABLE 5 Pharmacokinetic Profiles in the Rat AUC_(INF) T_(max) C_(max)(h-μmol/ T_(1/2) CI (mL/ V_(d) Ex. Mode (h) (μmol/mL) mL) (h) min/kg)(L/kg) Ex. 2B oral 1.67 0.42 1.91 2.72 431 112 i.v. NA 3.78 1.37 1.1141.4 3.94 Comp. oral 1.33 0.16 1.95 8.22 270 180 Ex. 3B i.v. NA 1.491.16 7.60 44.2 29.2 Comp. oral 0.67 0.48 1.28 3.44 1135 397 Ex. 4B i.v.NA 0.46 0.41 2.08 113 20.3 Ex. 3B oral 0.25 0.19 0.18 0.41 NA NA i.v. NA0.86 0.18 0.27 282 6.48 Comp. oral 0.38 0.07 0.12 0.95 NA NA Ex. 5B i.v.NA 2.68 0.42 1.33 154 17.8 Ex. 4B oral 0.83 8.73 33.2 3.58 NA NA i.v. NA2.92 3.07 1.47 15.2 1.91 Comp. oral 0.50 2.96 19.99 4.35 NA NA Ex. 6Bi.v. NA 1.41 1.34 2.36 34.9 7.04

1. A compound selected from the group consisting of:(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone,and(4-cyclopropyl-piperazin-1-yl)-[4-(2-hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-methanone,and enantiomers, and pharmaceutically acceptable salts thereof.
 2. Acompound that is(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone,or an enantiomer, or pharmaceutically acceptable salt thereof.
 3. Acompound that is(4-cyclopropyl-piperazin-1-yl)-[4-(2-hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-methanone,or an enantiomer, or pharmaceutically acceptable salt thereof.
 4. Acompound selected from the group consisting of:(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanoneand(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonedihydrochloride.
 5. A compound that is (4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone.
 6. A compound that is(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone dihydrochioride.
 7. Acompound that is(4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanonecitrate.
 8. A compound that is(4-cyclopropyl-piperazin-1-yl)-[4-(2-hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-methanonecitrate.
 9. A pharmaceutical composition comprising a pharmaceuticallyacceptable carrier and an effective amount of at least one compoundselected from the group consisting of: (4-cyclopropyl-piperazin-1-yl)-(4-morpholin-4-ylmethyl-phenyl)-methanone, and(4-cyclopropyl-piperazin- l-yl)-[4-(2-hydroxymethyl-morpholin-4-ylmethyl)-phenyl]-methanone, andenantiomers, and pharmaceutically acceptable salts thereof.
 10. Apharmaceutical composition according to claim 9, further comprisingtopiramate.